Field of the Invention
The present invention relates to an image forming apparatus configured to form an image on a recording material using an electrophotographic method, and more particularly, to a developing device and a process cartridge that are applied to the image forming apparatus.
Description of the Related Art
In an image forming apparatus such as a printer using an electrophotographic image forming method (an electrophotographic process), an electrophotographic photosensitive member (hereinafter referred to as a “photosensitive member”) serving as an image bearing member is uniformly charged, and the charged photosensitive member is selectively exposed to form an electrostatic image on the photosensitive member. The electrostatic image formed on the photosensitive member is visualized as a toner image using toner in a developer. The toner image formed on the photosensitive member is transferred onto a recording material such as a recording sheet or a plastic sheet, and the toner image transferred onto the recording material is fixed on the recording material by further applying heat and pressure thereto, thus image recording is performed.
Such an image forming apparatus generally requires supply of a developer and maintenance of various types of process units. To make the supply of the developer and the maintenance of the various types of process units easy, a photosensitive member, a charging unit, a developing unit, a cleaning unit, and others are collected in a frame as a cartridge. Thus formed process cartridge which is detachably attached to a main body of the image forming apparatus has been put into practical use. A process cartridge type enables an image forming apparatus superior in usability to be provided.
In recent years, a color image forming apparatus configured to form a color image using developers in a plurality of colors has widely used. As the color image forming apparatus, an inline type image forming apparatus has been known in which photosensitive members respectively corresponding to image forming operations using developers in a plurality of colors are arranged in line in a surface movement direction of an object to be transferred onto which a toner image is be transferred. The inline type color image forming apparatus includes one in which a plurality of photosensitive members is arranged in line in a direction (e.g., a horizontal direction) intersecting with a vertical direction (gravity direction). An inline type is an image forming type desirable in terms of easily coping with requests to increase an image forming speed and expand into a multifunction printer.
An inline type image forming apparatus in which a plurality of photosensitive members is arranged in line in a direction intersecting with a vertical direction includes one in which a plurality of photosensitive members is arranged below an intermediate transfer member serving as a member to be transferred or a recording material bearing member for conveying a recording material serving as a member to be transferred (see Japanese Patent Application Laid-Open No. 2003-173083).
In a case where the photosensitive member is arranged below the intermediate transfer member or the recording material bearing member, a fixing device and a developing device (or an exposure device) can be arranged at a distant, for example, in such a manner that the intermediate transfer member or the recording material bearing member is sandwiched therebetween within an image forming apparatus main body. Therefore, the developing device (or the exposure device) is not easily affected by heat from the fixing device.
On the other hand, if the photosensitive member is arranged below the intermediate transfer member or the recording material bearing member, as described above, a developer may be required to be supplied to a developing roller (developer bearing member) and a supply roller (supply member) against gravity. More specifically, a developing device configured to convey a developer from a developer containing unit arranged below the supply roller to the supply roller needs to be used. For the developing device thus configured, Japanese Patent Application Laid-Open No. 2003-173083 discusses a configuration for supplying sufficient toner against gravity from a developer containing unit to a supply roller. As illustrated in FIG. 7, in Japanese Patent Application Laid-Open No. 2003-173083, a supply roller (supply member) 50 rotates upward from below in a toner nip portion between a developing roller (developer bearing member) 40 and the supply member 50. Japanese Patent Application Laid-Open No. 2003-173083 discusses a method for bringing a receiving sheet 400 into contact with the lower side of the supply member 50 as a unit for supplying a developer to the supply member 50. According to this method, the receiving sheet 400 prevents the developer, which has adhered to the supply member 50, from dropping by gravity, to prevent a solid image from decreasing in density in such a manner that the developer, which can be supplied to the developer bearing member, does not decrease.
According to a configuration discussed in Japanese Patent Application Laid-Open No. 2003-173083, an additional member such as a receiving sheet needs to be provided on the lower side of the supply member 50 to sufficiently supply the developer from the developer containing unit arranged below the supply member 50 to the supply member 50, so that the configuration of the image forming apparatus becomes complicated.
Therefore, the present invention is directed to preventing a solid image from decreasing in density in a simple configuration in a developing device configured to convey a developer from a developer containing unit arranged below a supply member to the supply member.